(1) Field of the Invention
This invention relates to intercell connections for electrochemical cells and more particularly to such intercell connections for lead-acid batteries.
(2) Description of Related Art
A typical electrochemical battery is divided into cells with partition walls that are molded into the battery container. Each cell contains at least one pair of oppositely charged electrode plates, at least one separator and electrolyte. To connect the cells together, there are essentially two approaches presently utilized by the battery manufacturing industry.
The first approach involves welding together two lead connectors situated on either side of a partition wall. The weld is made by penetrating the partition wall. The hole made in the partition wall is mechanically sealed by the displacement of lead from the two connectors which form a intercell connection nugget. This mechanically derived seal prevents battery acid leakage through the weld/partition wall interface. This is known as a through-the-partition weld.
The second approach involves welding the connectors together over the top ends of the partitions. After the welds are made, the cells are sealed with an epoxy. This is known as an over-the-partition weld.
Though each approach has advantages, each also has its share of drawbacks. The through-the-wall weld approach is cost effective and can be produced with standard battery weld equipment. Unfortunately, in order to have uniform, effective heat sealing, the heat seal has to be restricted to a common plane. The weld is formed below this plane on the partition walls. Above this plane is an area known as head space. Battery pressure release valves, terminals and passive short protection are located in the head space. However, due to the heat seal restriction, the weld cannot be formed in the head space thereby resulting in a waste of limited head space. To accommodate the weld and the components located in the head space, the head space has to be made excessively large.
The over-the-partition weld solves the wasted head space problem since the weld connections are made in the same head space occupied by the battery valves, terminals and passive short protection. However, this approach is more costly in terms of equipment and ease of manufacture. To accomplish this weld, nonstandard equipment has to be used. To create a hermetic seal between the cells, a low viscosity, self-leveling epoxy has to be used to encapsulate the welds. This operation has to be performed with the battery oriented on the manufacturing line in an inverted position.
Accordingly, there is a need in the industry for a cost effective approach to connect battery intercells without adding head space and without having to invert the battery during manufacture.